I have a small room with dimensions: 3.55m L x 2.1m W x 2.35m H, needed for human speech. I have used 17m2 of acoustic absorption panels with NRC of about 1.05. Also, I measured the Rt60before treatment it was about 1.2s before treatment and became 0.2 after treatment. I have distributed the 17m2 of acoustic panels almost evenly over ceiling and the three wall. The forth wall left blank [Gypsum Board] to be background for the talker.

I am wondering when we started recording the sound, still the human voice is strong. Not as strong as it before treatment but still strong. Would anyone inform me what might be the reason behind this strong voice??? Do I have to use more panels??? is the geometry of room bad enough to cause this distortion even after treatment???

Measuring reverberation is of no use in such a small room.Reverb is a soundfield that's stochastic, so you have no direction, and it is calculated after the initial sound is down 5 dB. In a small room this is meaningless.You could measure if there are resonances in the room sustaining certain frequencies in the vocal range.

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